Voltage instability has played a major role in at least two of the recent major blackouts in North America, namely the Jul. 2, 1996 Western American blackout and the Aug. 14, 2003 Northeastern blackout. Voltage instability was encountered in these two blackouts because reactive power supplies such as generator reactive power outputs and shunt capacitor devices were exhausted ahead of the eventual blackouts.
Unlike active power, which can flow from sources to sinks over long transmission paths, reactive power must be supplied and balanced locally to meet the reactive power demands at load centers. Reactive power losses over transmission lines and transformers are typically several factors higher than active power losses. It is well known that voltage stability phenomena tend to be local while active power phenomena may involve geographically widespread operational domains. Although there is a breadth of theoretical analysis of voltage stability is relatively well understood, there exist only a few methods and devices for monitoring and mitigating voltage instability in a real-time operational environment.
The present description provides for the calculation of the value of reactive power load when changes in reactive power outputs of at least some of the generators in the electrical power system cause all of the generators on the system to reach the combined operating limit of their reactive power output.
These and other desired benefits of the preferred embodiments, including combinations of features thereof, will become apparent from the following description. It will be understood, however, that a process or arrangement could still appropriate the claimed invention without accomplishing each and every one of these desired benefits, including those gleaned from the following description. The appended claims, not these desired benefits, define the subject matter of the invention. Any and all benefits are derived from the multiple embodiments of the invention, not necessarily the description in general.